Self-Reactivated Mesostructured Ca-Al-O Composite for Enhanced High-Temperature CO2 Capture and Carbonation/Calcination Cycles Performance

Abstract

In this study, highly efficient high-temperature CO2 sorbents of calcium aluminate (Ca-Al-O) mesostructured composite were synthesized using presynthesized mesoporous alumina (MA) as a porous matrix to react with calcium nitrate through a microwave-assisted process. Upon annealing at 600 degrees C, a highly stable mesoporous structure composed of poorly crystalline Ca(12)A(14)O(33) phase and the CaO matrix was obtained. The Ca-Al-O mesostructured sorbents with a Ca2+/Al3+ ratio of 5:1 exhibit an enhanced increasing CO2 absorption kinetics in the CO2 capture capacity from 37.2 wt % to 48.3 wt % without apparent degradation With increasing carbonation/calcination cycling up to 50 at 700 degrees C due to the strong self-reactivation effect of the mesoporous Ca-Al-O microstructure. Remarkable improvements in the CaO-CaCO3 conversion attained from the mesostructured Ca-Al-O composite can be explained using the concept combined with available mesoporous structure and Ca12Al14O33 phase content. However, a high Ca2+/Al3+ =8:1 Ca-Al-O composite causes degradation because the pores become blocked and partial sintering induces CaO agglomeration.